A Local Area Network (LAN) is commonly used in enterprise networks, campus networks, etc. Ethernet, which is a name for a family of LAN technologies standardized by the Institute of Electrical and Electronics Engineers (IEEE) (IEEE 802.3 standard), is one of the most popular and useful techniques for building LANs.
A typical LAN is configured with switches and transmission lines connecting between the switches. The lines are co-axial cables, Unshielded Twisted Pair (UTP) cables or optical fibers. If the lines are optical fibers, because the switches handle electrical signals, port interfaces of the switches have optical/electrical converters and electrical/optical converters.
A VLAN is a broadcast domain whose members communicate with each other as if they shared the same segment even of the members are in different physical LAN segments from each other. In other words, a VLAN is a logical LAN segment.
There are several types of VLANs in the IEEE 802.1Q standard. One of them adds a VLAN identifier (VLAN tag) to a frame, where the frame is sometimes called a tagged frame. FIG. 9 illustrates one example of a tagged Ethernet frame. The destination and source addresses are destination and source MAC (Media Access Control) addresses, respectively. The VLAN protocol identifier is a field with a value of “0×8100”. When the field contains the value, the frame is a VLAN tagged frame. The priority is a field indicating the user priority of the frame. CFI stands for Canonical Format Indicator. Canonical format refers to the bit-ordering (Little or Big Endian) of the bytes within a frame. VLAN identifier is a 12-bit field. Both the values of all ones and all zeroes are not available for a VLAN ID, so the maximum number of VLANs identified by the VLAN ID is 4,094. FIG. 18 depicts one simple example of network configuration with VLAN ID. No frame with VLAN ID=1 is forwarded to any member of the VLAN 2.
Recently, Ethernet has come into use in Metropolitan Area Networks (MANs) and Wide Area Networks (WANs) of network carriers. Network carriers control network operation in MANs/WANs and provide communication services between LANs connected to each other by the MANs/WANs. The network carriers may want to provide services like Virtual Private Networks (VPNs). Virtual metropolitan area networks (vMANS™) by Extreme Networks® realize such services. The vMANs scheme is shown in the tech brief entitled “Extreme Networks Virtual Metropolitan Area Networks” by Extreme Networks. In short, vMANs use a tunneling technique with tags called vMAN tags like VLAN tags (VLAN IDs) in the IEEE 802.1Q standard. FIG. 19 shows a concept of the vMAN scheme.
Wavelength Division Multiplexing (WDM) technique is known. The WDM is a technique to multiplex light signals of a plurality of channels over an optical fiber by using a light filter. It makes a larger transmission capacity of an optical fiber.
One of the advantages of the typical LAN with switches is that it can support Virtual Local Area Networks (VLANs), which is the IEEE 802.1Q standard. Rich Seifert, “The Switch Book”, John Wiley & Sons, Inc., Chapters 11 and 12, gives details about VLAN technique.
The U.S. Pat. No. 5,572,347 relates to a switched video architecture and it shows an integrated fiber optic telecommunications network providing switched video and standard narrow band telephone services. Frequency division multiplexing of the narrow band telephone service and control signals with EM channels for video distribution is used.
The U.S. Pat. No. 6,269,098 B1, to Crayford, issued Jul. 31, 2001, routes VLAN packets. The address table includes a virtual local area network index field. A decision making engine receives a VLAN ID from a packet or frame, converts it to a VLAN index and searches an address table for data forwarding information based on the generated VLAN index. The maximum number of VLANs supported is the VLAN capacity. The capacity is increased or decreased by changing the size of the VLAN field.
The U.S. Pat. No. 5,963,556, to Varghese et al, issued Oct. 5, 1999, divides a large extended LAN into multiple VLANs interconnected by routers by dividing bridge ports into virtual LANs.
The U.S. Pat. No. 6,035,105, to McCloghrie et al, issued Mar. 7, 2000, is related to the problem of VLAN identification within a packet when a frame is bridged or routed from a first type of VLAN to a second type of VLAN.
The U.S. Pat. No. 6,085,238, to Yuasa et al, routes data in a VLAN using predefined traffic bands or frequencies, with a routing table that links group IDs with specific frequencies.
The U.S. Patent Application Publication to Kloth, US2001/0005369 A1, published Jun. 28, 2001, uses the received frame type designation or receiving port in constructing a derived VLAN value.
The patent to Linden, WO01/93480 A1, published Dec. 6, 2001 discusses Wavelength Division Multiplexing (WDM) and the use of VLANs.